July 29, 2009 -- If swine flu vaccine is in short supply -- nationally or in local areas -- pregnant women and people caring for or living with infants will go to the front of the line, the main U.S. vaccine advisory committee today recommended.

The Latest on H1N1 Swine Flu

Next would come health care workers and first responders who have direct contact with patients, children 6 months to 4 years old, and kids 4 to 19 years old with medical conditions that put them at risk of severe flu disease. There are about 42 million Americans in these groups.

Plenty of Swine Flu Vaccine?

By the end of October, officials expect to have 120 million doses of swine flu vaccine on hand. That's not enough for everybody -- especially if two doses are needed -- but that would be enough to add more people to the front of the line.

If projected vaccine supplies are on hand, otherwise healthy children 4 and older would be included in the first group to get the vaccine. People 25 to 64 with underlying medical conditions that put them at risk of severe flu disease would also be included, as would a larger group of health care workers and emergency medical technicians.

Once there's enough vaccine for these urgent groups, swine flu vaccine will be offered to healthy people 24 and older.

But not everyone agrees that the vaccine should be doled out one group at a time. The 120 million doses of swine flu vaccine that should arrive by the end of October is more doses of flu vaccine than Americans have ever used in a single year.

"The only sin is vaccine left in the refrigerator. And this happens every time you prioritize flu vaccine," William Schaffner, MD, president-elect of the National Foundation for Infectious Diseases, told the committee.

Swine Flu Vaccine: Full Speed Ahead or Go Slow?

The recommendations came today in a special, urgently called meeting of the CDC's Advisory Committee on Immunization Practices, a group of vaccine and infectious disease experts from outside the CDC. The group's recommendations are almost always made official U.S. vaccine policy by the FDA and CDC.

The next wave of the H1N1 swine flupandemic is expected to hit the U.S. this fall. Early vaccine supplies -- about 40 million doses -- could become available as early as September.

That will happen only if officials decide by mid-August to start packaging swine flu vaccine without waiting for initial safety and efficacy data from clinical trials. Those trials have just begun. The earliest information from those trials won't be available for six to eight weeks.

The new flu vaccine will be the second flu vaccination Americans will be urged to get. This year, even more than others, health officials will be urging us to get our annual flu vaccine to protect against seasonal flu. Soon after that, we'll be asked to line up to get our swine flu vaccination.

"This year our challenge has doubled," HHS Secretary Kathleen Sebelius said in a video feed to the meeting. "Like seasonal flu, the novel H1N1 flu is deadly. ... It has spread wide and disrupted communities across the U.S. While media attention has decreased over the summer, the threat from this virus has not."

We may very well be asked to get two shots of swine flu vaccine. CDC flu expert Anne Schuchat, MD, says the CDC expects immunization to require two shots, given three weeks apart. It's not yet clear whether the inhaled version of the swine flu vaccine will require two doses or just one.